Liquid crystal display devices have been used in various fields because of its thin profile, lightweight, and low power consumption characteristics and the like, and are commonly used, in recent years, in mobile devices such as a cellular phone. Such LCD devices are often used in outdoor environments, and in such environments, prevention of reflection of ambient light and reduction in power consumption need to be achieved. Therefore transflective liquid crystal display devices in which both ambient light and a backlight can be used for display have been developed. The transflective LCD devices can provide display in both a transmissive mode and a reflective mode.
When transflective LCD devices are normally black vertical alignment (VA) LCD devices, a λ/4 retarder is arranged in a reflective display region of the LCD device for performing effective reflective display. The λ/4 retarder gives a retardation of λ/4 between two polarization components that oscillate in mutually-perpendicular two directions of transmissive light having a wavelength of A, whereby the transmissive light is converted into circularly polarized light. The λ/4 retarder is arranged in the reflective display region and polarizing plates are arranged in cross-Nicol. According to this configuration, the polarizing plate disposed on a viewing side can block light that has entered from a viewing side and then reflected from the reflective display. Thus normally black display can be provided.
However, when a λ/4 retarder is arranged in a transflective LCD device, a circularly polarizing plate including a linearly polarizing element and a λ/4 retarder is generally attached over the entire viewing-side surface of the liquid crystal display panel. In this case, the λ/4 retarder is arranged not only a reflective display region but also a transmissive display region. Therefore, unneeded retardation is given to transmissive light by the λ/4 retarder arranged in the transmissive display region, which might cause reduction in contrast ratio, luminance, and the like of transmissive display.
An approach for eliminating the unneeded retardation given to the transmissive light by the viewing face-side λ/4 retarder by arranging a λ/4 retarder also on a back side of the LCD device has been developed. However, in the approach, retardations given by the λ/4 retarders on the respective sides need to be accurately matched, and therefore the accuracy of the production process needs to be improved. This need leads to an increase in costs, and in this aspect, the approach needs to be improved. According to the approach, two λ/4 retarders are used, which leads to an increase in costs and thickness of the panel. Also in this aspect, the approach needs to be improved.
Patent Document 1 discloses, for example, a technology for forming a λ/4 retardation layer only in a reflective part of a liquid crystal display device. The LCD device in accordance with Patent Document 1 includes the λ/4 retardation layer in the reflective part but not in a transmissive part, and therefore light does not pass through the λ/4 retardation layer in the transmissive part. As a result, a reduction in contrast ratio in transmissive display can be prevented.
Further, Patent Document 2 discloses a liquid crystal display device including a multilayer structure where a first substrate having a reflective layer, a liquid crystal layer, a second substrate, and a polarizing plate are stacked in this order from a back face to a display face. According to this LCD device, the first substrate includes a retardation layer between the reflective layer and the liquid crystal layer or in a region free from the reflective layer, or the second substrate includes a retardation layer. This retardation layer has two or more regions giving different retardations in a display face plane. According to this, retardation can be compensated in accordance with the respective display modes.
[Patent Document 1]
Japanese Kokai Publication No. 2003-322857
[Patent Document 2]
WO 2007/063629